"This controls the size of the world map" as it says at the bottom of the screen when this option is highlighted. Also at the bottom of the screen is shown the dimensions of the world that will be generated given the currently selected size. Using Basic World Generation, the size options are:

Pocket (17x17 region tiles)

Smaller (33x33)

Small (65x65)

Medium (129x129)

Large (257x257)

Setting this to a larger value will cause world generation to take longer, as more events will need to be calculated per step.

"This is the length of pre-generated history." The number of years for the currently selected length will be shown in the lower right. Essentially this means the amount of time that civilizations will have to grow, attack each other, and starve to death. It also determines the amount of time that megabeasts will have to roam and kill things, get killed, etc. The longer the history, the more historical events will be generated.

Setting this parameter to a higher value will cause world generation to take longer as more events need to be determined. Setting it to a very low value is ok, but will reduce the size of civilizations.

Higher values will also increase the number of abandoned (sacked) towns and fortresses which can matter for adventure mode, but doesn't matter that much for fortress mode. Recommend value for worlds you plan to use for adventure mode are Short or Medium.

For more information on the history aspect of the game, see Legends and Ages.

This controls the number of megabeasts such as dragons, titans, etc., that exist at the beginning of the world. They can later die (get killed) due to historical events, so the longer the history the more likely some of these will die.

The number of beasts does not appear to impact how often your fortress will be attacked by beasts in fortress mode. In adventure mode it means it will be easier to find more megabeasts. If set very low then you may actually run out of beasts during a game.

Since beasts can attack civilizations, more beasts may reduce the population of the world a little bit.

Increasing this value increases the number of savagebiomes in the world. In short, this means that more areas are likely to have aggressive animals which may try to kill dwarves immediately upon embark and attack adventurers more often while traveling.

New players may want to just leave this at the Medium setting (which isn't that hard) or set it lower. Turn this up to make the game more fun.

This is a rather important parameter for fortress mode. Sparse means that many areas will only have one or two types of metal ore, if any, which can be very annoying to people until the economy is fully implemented and other metals can more easily be obtained via trade. New players should probably turn this up to Frequent.

In adventure mode this can impact the types of metals that civilizations have access to, which can affect the types of items that are available in shops. Therefore it may not be a bad idea to turn this up for worlds in which you plan to play adventure mode games.

You may notice that during various phases of the world generation process worlds will be rejected, leading to the rejection count going up and the process starting over. This happens because certain factors such as number of mountain tiles can't be determined ahead of time by the generation process. Instead worlds are generated with parameters which are likely to produce worlds that can support a required number of mountains, and are then checked to make sure they meet the criteria. For example, the random generation of the topography of the land may result in too few high elevation areas to place mountains.

In practice you don't need to worry about this for basic world generation because the preset hidden values that determine acceptable criteria are designed to decrease the chance of rejections, but certain combinations of basic parameters (especially with very large worlds) may make it harder for the process to generate "acceptable" worlds. Basically what this amounts to is that world generation will just take longer for certain parameter selections that are more difficult for the generator to satisfy.

Once the world itself has been generated, the process of generating historical events will begin. This can take a very long time for large, heavily populated worlds with very long 2,000 year histories.

Once everything is complete, you can take a look around using the directional keys. (Using Shift+directional key will make this faster.) If you find yourself confused about what all the characters actually mean, you are not alone. Check out the Map legend. At this point you can either abort the process or hit Enter to save the world to disk.

Unfortunately the post-generation-process viewer doesn't give you a way to view much information about the world, so unless you really hate the look of the map or something you probably want to just save the world and load it up in Legends mode to view more information.

At first you will probably be satisfied with basic world generation, but later you may find that you want to create worlds with specific more extreme conditions. Check out the documentation on Advanced world generation for help with this.

On the 86th rejected world an error report will appear with four options, this is in reference to the term "86ing" something, which is defined in the Urban Dictionary as "To remove, end usage, or take something out or away." [1]